1. Field of the Invention
The present invention relates to a rotating device having a thrust fluid dynamic pressure bearing, a manufacturing method of the rotating device, and a bearing component thereof.
2. Description of the Related Art
Rotating devices like hard disk drives are becoming compact and increasing the capacity, and loaded in various electronic devices. In particular, loading of disk drive devices in portable electronic devices, such as a laptop computer and a portable music player, is advancing. Rotating devices like disk drive devices loaded in such portable electronic device need thinning and weight saving, and also improvement of the rigidity of the rotating devices in order to withstand against a vibration at the time of carrying in comparison with the rotating devices loaded in a stationary electronic device like a desktop computer. In general, thinning of rotating devices and improvement of the rigidity thereof are in a trade-off relationship.
The inventor of the present invention propose, in JP 2011-153705 A, a rotating device that has an improvement in an efficiency of collecting the lubricant in a thrust dynamic pressure generating part, thereby enhancing the dynamic pressure. The rotating device of JP 2011-153705 A includes thrust dynamic pressure patterns formed by pressing a mold against a patterning target, such as a rotating body or a stationary body. According to such a rotating device, the collapsing of the shapes of the concavities of the formed thrust dynamic pressure pattern and the convexities thereof and the unevenness in height of those concavities and convexities can be suppressed.
In order to downsize the rotating device having a dynamic pressure generation part, a component configuring the dynamic pressure generating part may be downsized. When, however, the dynamic pressure generating part is downsized, the area of the dynamic pressure generating part is reduced, and thus the bearing rigidity decreases. This results in a negative effect to the shock resistance of the rotating device and the vibration resistance thereof. Such rotating devices have a stationary body and a rotating body, and when the bearing rigidity decreases, respective faces of the stationary body and the rotating body in the rotation axis direction may contact with each other when a shock like falling is applied to the rotating devices. When the rotating body contacts the stationary body, the performance is deteriorated, contact sounds are produced, or the contacting portion is worn out, resulting in the reduction of the lifetime of the rotating devices.
In order to compensate such a reduction of the bearing rigidity, a gap with the dynamic pressure generating part may be reduced. When, however, the gap is reduced, the bearing loss increases, and power consumption may increase in some cases. Alternatively, the dynamic pressure generating part may be deformed by processing pressure when the dynamic pressure generating part is processed. For example, when a mold is pressed against an end face of a cylindrical member having an inner circumferential surface that encircles a shaft and retains the shaft therein in the axial direction, a deformation such that the inner circumferential surface of that member expands inwardly may occur. When a radial dynamic pressure generating groove is formed in this inner circumferential surface, the radial dynamic pressure generating groove may be deformed, which may negatively affect the formation of dynamic pressure. Moreover, when the inner circumferential surface is deformed, the inner circumferential surface and the retained shaft highly possibly contact with each other during a relative rotation. When a contact occurs during a rotation, it may be a cause of the deterioration of the performance, a generation of contact sounds, or a worn-out of the contacting portion. Furthermore, when a work is carefully carried out so as not to cause the inner circumferential surface to be deformed, the work efficiency becomes poor.
In order to compensate such a reduction of the bearing rigidity, a groove pattern that can efficiently generate dynamic pressure may be derived through a computer simulation and employed. An example groove pattern derived through a computer simulation has a change in the width of the groove and the depth thereof. Another example groove pattern derived through a computer simulation has the groove pattern miniaturized in comparison with conventional technologies. However, according to the conventional manufacturing technologies, it is difficult to stably produce a groove having a width and a depth changed and a groove employing a miniaturized structure. Alternatively, the processing of the groove in such a shape needs a large labor work, resulting in a decrease of the work efficiency.
Such disadvantage is not only for rotating devices loaded in portable electronic devices, but also for rotating devices loaded in electronic devices of other kinds.
The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a rotating device including a thrust dynamic pressure generating groove that can suppress a reduction of a bearing rigidity and a manufacturing method thereof and a bearing component.